<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>hello千锋</title>
  <style>
    
  </style>
</head>
<body>
  <form action="">
    1
    <input type="text">
    <select name="" id="">
      <option value=""></option>
    </select>
    <textarea name="" id="" cols="30" rows="10"></textarea>
  </form>
  <form action="">2</form>
  <form action="">3</form>
  <form action="">4</form>
</body>
<script>

  // 根节点
  console.log( document );
  // html标签
  console.log( document.documentElement );
  // head标签
  console.log( document.head );
  // body标签
  console.log( document.body );
  // 页面上所有的表单标签
  console.log( document.forms );
  // 某个表单内的所有表单控件标签
  console.log( document.forms[0].elements );
  console.log( document.forms[1].elements );

  // 操作title的内容
  console.log( document.title );
  document.title = "123";
  
</script>
</html>